my 98 tj came witha d44 in the rear and 30 up front.. when i blew out the ring gear on my d44 i drove in 4 high for about a month so basiclly just on the d30 .. and it did apsolutly no harm waht so ever.. i also have dana 30 front and rear in my 83 s-10 and it has no problems with breaking what so ever so take that for what its worth